Improving the light extraction efficiency of a light-emitting device is a heavily competed research subject in this field.
However, for a light-emitting device including a flip-chip, the light emitted from the lateral side of the chip structure cannot be guided out easily, and therefore the device as a whole has lower light extraction efficiency. Accordingly, to increase the brightness of the device, it is known to adopt a process such as substrate lift-off, for example, laser lift-off (LLO) or surface roughening, or to provide a film having a wavelength conversion function between the lateral side of the chip structure and the reflective structure. However, the above process incurs high manufacturing costs, suffers from the disadvantage that the film has limited heat resistance, and therefore a high power requirement cannot be satisfied. In fact, a film with a wavelength conversion function tends to have a larger light decay when at a high light-emitting density, and thus is not suitable for use in a harsh environment. Furthermore, the brightness improvement of a light-emitting device adopting the above means is still limited.